Recently, the demand for portable electronic products such as notebooks, video cameras, cellular phones or the like has rapidly increased, and electric vehicles, energy storage batteries, robots, satellites have been actively developed. For this reason, high-performance secondary batteries allowing repeated charging and discharging are being actively studied.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. When being used for such middle-sized or large-sized devices, a great number of secondary batteries are electrically connected to enhance capacity and output. In particular, for such middle-sized or large-sized devices, pouch-type secondary batteries are frequently used since they may be easily accommodated and stacked. A battery module may mean a component in which a plurality of secondary batteries is connected in series or in parallel to enhance capacity and output as described above.
When configuring such a battery module, one of main issues is cooling. A secondary battery may generate heat by itself while repeating charging and discharging, and since a plurality of secondary batteries is concentrated in a narrow space of a battery module, the temperature of the battery module may greatly rise while the battery module is in use. Further, since middle-sized or large-sized devices such as vehicles and power storage devices are frequently used outdoors, the temperature of the battery module mounted thereto may more greatly rise under a high-temperature situation, for example in summer. However, if the temperature rises over a suitable level, the secondary battery included in the battery module may exhibit deteriorated performance and, in severe cases, may be fired or exploded. Therefore, it is a very important issue to ensure cooling performance when configuring a battery module.
A cooling method of a battery module is representatively classified into two types: air cooling and water cooling, and the air cooling type is widely used in comparison to the water cooling type due to electric short and waterproofing of a secondary battery. For the air cooling method, in many cases, a duct is provided to introduce fluid, for example an external air, into a battery module and discharge an air in the battery module to the outside.
In the configuration of such an existing battery module, air flows in or out through inlet and outlet ports of a duct, and in this process, external impurities such as dust and moisture may penetrate through the inlet and outlet ports of the duct. In this case, impurities such as moisture and dust may become a cause of deteriorating or breaking the battery module, and may also block a coolant path in the battery module to deteriorate cooling efficiency. Moreover, an electrically conductive substance such as bolt and wire piece may penetrate into the battery module through the inlet and outlet ports of the duct as an impurity, and in this case, such an electrically conductive substance may contact an electrode tab or a terminal to cause a short circuit in the battery module, which may break the battery module or cause fire or explosion.
To solve this problem, in an existing technique, a distance between the inlet and outlet ports of the duct is reduced, or a wire mesh or filter is installed at the inlet and outlet ports. However, such structures may disturb the flow or air through the inlet and outlet ports of the duct, which may cause a sufficient amount of air not to flow in and out through the duct, thereby seriously deteriorating the cooling performance of the battery module.